Etchells

Etchells (El) has pointed out that the Baker chart has four major shortcomings (1) the data used to define the flow patterns are based upon the independent visual observations of many researchers, each having his own description for a particular flow pattern (2) air-water measurements in 1-and 2-in. pipes represent a major portion of the data (3) the chart is prepared from a limited number of data, not all taken at the transition points and (4) many experiments were performed in short pipes or pipes with unusual inlets, causing entrance and transition effects that may not have died out in the region of observation. Similar comments can be made about the other flow pattern charts. 

Additional research on the prediction of flow patterns is a necessity, for until detailed stability criteria are developed for the transition from one flow pattern to another, there is no alternative to the empirical flow pattern charts. Some progress in theoretically defining the transition from stratified to wavy or slug flow has been made by Russell and Etchells (R3). Inaccuracy and uncertainty in flow pattern prediction makes estimation of the in situ hydrodynamic quantities and the rate of heat transfer a difficult task. 

All solutions of Eqs. (3) such as that by Yu and Sparrow (Yl) yield the velocity profiles in each phase as a function of the interfacial position h and the pressure drop. The volumetric flow rates Qt and Q are obtained by integrating each velocity profile over the respective phase cross-sectional area. The ratio of the flow rates can then be determined as a function of only the interfacial position, and since the volumetric flow rates are known, this yields an implicit fourth order equation for the interfacial position h. The holdups Rt and Rn can be calculated once the interfacial position is known. Since each equation for the volumetric flow rates is linear with respect to the pressure drop, once the interfacial position is known the pressure drop may be easily computed. An analytical procedure for determining pressure drop and holdup for turbulent gas-laminar liquid flows has been developed by Etchells (El) and verified by comparison with experimental data in horizontal systems (A7). 

R3. Russell, T. W. F., and Etchells, A. W., Paper presented at Int. Symp. Two-Phase Systems, Haifa, Israel, August, 1971. 

O. Renault, O.V. Salata, M. Etchells, P.J. Dobson, and V. Christou, A low reflectivity multilayer cathode for organic light-emitting diodes, Thin Solid Films, 379 195-198, 2000. 

Baldyga, J., J. R. Bourne, B. Dubuis, A. W. Etchells, R. V. Gholap, and B. Zimmerman (1995). Jet reactor scale-up for mixing-controlled reactions. Transactions of the Institution of Chemical Engineers 73,497-502. 

Etchells, J. (2001). "Prevention and Control of Exothermic Runaway An HSE Update." Loss Prevention Bulletin, 157 (February), 4-8. 

Etchells AW, Ford WN, Short DGR. Mixing of Bingham plastics on an industrial scale. In Fluid Mixing III, Symposium Series 108, Institution of Chemical Engineers. Rugby, UK Hemisphere Publ. Corp., 1985 271-285. 

J C Etchells, T J Snee and A J Wilday, "Relief System Sizing for Exothermic Runaway The UK HSE Strategy", International Symposium on Runaway Reactions, Pressure Relief Design and Effluent Handling, 135-162, AiChE, 1998, ISBN 0-8169-0761-7... 

Prepared by Janet Etchells Gas and Chemical Process Safety Unit Directorate of Science and Technology Health and Safety Executive and Jill Wilday Process Safety Section Health and Safety Laboratory Health and Safety Executive... 

J.C. Etchells. Prevention and control of exothermic runaway. In Proc. Conference on Assessment and Control of Chemical Reaction Hazards, IBC, London, 1993. 

Etchells, A.W. Slurry-Handling Problems in the Process Industries in Processing of Solid-Liquid Suspensions, Shamlou, P.A. (Ed.), But-terworth-Heinemann Boston, 1993, pp. 310— 322. 

Short, D.G.R. Etchells, A.W. Proceedings of the Fourth Europ. Conference on Mixing, April 27-29 1982, (BHRA Fluid Engineering), Paper A1, 1-10... 

Capecchi S., Renault O., Moon D.Y., Halim M., Etchells M., Dobson P. J., Salata O. V. and Christou V., High-efficient organic electroluminescent devices using an organoterbium emitter, Adv. Mater. 12 (2000) pp. 1591-1594. 

Cornish PL, Knowles SR, Marchesano R, Tam V, Shadowitz S, Juurlink DN, Etchells EE. Unintended medication discrepancies at the time of hospital admission. Arch Intern Med 2005 165 424-9. 

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